British Prime Minister David Cameron says Scotland's decision to release the Lockerbie airliner bomber was ''completely wrong" but adds that he does not believe energy giant BP should be blamed for the release.

Cameron, speaking at a joint news conference in Washington with U.S. President Barack Obama, said the Scottish government alone was responsible for the freeing one year ago of Abdelbaset Ali al-Megrahi.

The Libyan had been imprisoned in Scotland following his conviction in connection with the 1988 bombing of a U.S. passenger jet over the Scottish town of Lockerbie that killed 270 people, the majority of them Americans.

Reports have suggested that British-based BP lobbied for the release of al-Megrahi in exchange for a lucrative oil deal with Libya.

But Cameron said he had seen no evidence that Scotland's decision to release the cancer-stricken Libyan on compassionate grounds was influenced by BP.

"The role of BP and any lobbying they might have done is an issue for BP and an issue they should explain themselves,” Cameron told reporters at the White House.

Cameron said he hasn’t “seen anything to suggest that the Scottish government was in any way swayed by BP. They were swayed by their considerations about the need to release him on compassionate grounds -- grounds that I think were completely wrong. I don't think it's right to show compassion to a mass murderer like that. I think it was wrong."

Cameron, however, also ruled out demands by U.S. lawmakers for a formal inquiry into the issue.

Scotland forms part of Britain, but under Britain's devolved system of government, Scottish ministers have control over justice matters.

BP has already been facing widespread criticism in the United States over its handling of the enormous oil leak that occurred following an explosion at one of its platforms in the Gulf Of Mexico in April.